A gearbox for an aircraft primarily functions to transmit rotational power through fixed engagements. A common gearbox lube system lubricates and removes heat, where lube oil is typically sourced from an external pumping system and is distributed within the gearbox. However, sometimes multiple functionalities are required that can be difficult to incorporate together and then package into the gearbox. These functionalities can include gearbox lubrication and cooling, a clutch to engage and disengage the gearbox, control of a propeller blade pitch system, and electrical systems with control and sensing capabilities.
Where higher capability and system functionality are necessary, a higher level of complexity and integration effort is required. In addition, a gearbox for an aircraft typically needs to operate at multiple altitudes. These altitudes usually require various aircraft angles and sometimes zero to negative G operation, especially for military aircraft. A typical gearbox is commonly designed with these multiple altitudes in mind. However, implementing multiple systems in a gearbox has been traditionally been challenging.